title: Sampling and questionnaires.
authors.affiliation: Area de Pediatría. Universidad de Murcia. El Palmar. Murcia. Spain. virperez@um.es
authors.forename: V
authors.initials: V
authors.lastname: Perez-Fernandez
mesh_terms: D003627:Data Interpretation, Statistical; D006801:Humans; D012107:Research Design; D012494:Sampling Studies; D012984:Software; D011795:Surveys and Questionnaires